A serum potassium level above 10 mmol/l in a patient predisposed to hypokalemia

Background A 58-year-old man, previously diagnosed with Bartter's syndrome, presented with a short history of vomiting, diarrhea and weakness. He had severe hyperkalemia (serum potassium levels > 10 mmol/1), which was successfully managed. Post hoc investigation suggested that the patient had Gitelman's rather than Bartter's syndrome. Investigations Physical examination, urine and blood analyses, chest radiography, electrocardiogram, renal ultrasound, and genetic analysis focusing on the SLC12A3 gene, which encodes the thiazide-sensitive Na/CI cotransporter. Diagnosis Gitelman's syndrome and hyperkalemia secondary to acute renal failure plus exogenous potassium supplementation. Management Intravenous calcium gluconate, insulin and dextrose administration. Temporary continuous venovenous hemodiafiltration. Genetic confirmation of the underlying molecular defect. Long-term treatment for Gitelman's syndrome with oral potassium and magnesium supplements and epithelial sodium channel-blocking drugs. Review of patient education regarding renal salt-wasting syndromes.